I have a little pond, about 4' x 7' and about 18" deep. It has a waterfall/stream that's longer than it is. We've had it for several years, having put it in when I was pregnant with my now 7-year old (just didn't tell my doctor how I was getting my exercise LOL!) Not being sure how they would do, I put some "feeder goldfish" from the pet store in there. Some of them lived for several years, before a Blue Heron had them for lunch. I'm glad I didn't invest in something fancy! It's been a real popular spot for the local frogs, especially during last year's drought. A lot of birds use it as a watering hole, and bathe in the stream when it is running.
I guess with all the frogs in there, this was inevitable. Today we spotted a snake among the water lilies. We have tentatively identified it as a Red bellied Water Snake, Husband has escorted it off the premises. Yep, he's a nut!